when the rear sight has started to run.
What's the trouble?
If the elev is not holding in position, then just tighten the 'nut' in the windage knob 1 click clockwise - pushing inward on the screwhead in the elev knob will make it easier to turn the nut with a suitable flat blade screwdriver.
The windage knob should require 'firm', but not 'hard' finger pressure to make it rotate. Also, pushing inward on the elev screw will make it easier to rotate the windage knob.
Also make sure the screw in the elev knob is tightened firmly - otherwise the elev knob will 'ratchet' without moving the aperture ramp up/down.
Another possible problem is that the nub on the elev drum that rides on the serrations might be worn smooth - the elev clicks should be crisp - not 'mushy'.
The ball & spring is SAI way of providing the 1/2 moa windage changes. The rest of the sight is similar to USGI on M1. I doubt that the rear sight needs to be disassembled unless the trouble is the nub on the elev drum. If you DO disassemble be ready to catch & hold the ball & spring, and note how they are installed for reassembly.
Endwell NY USA